Langley's writings include:
- The Land of the White Elephant: Experiences in Indo-China (1892)
- In Savage Lands: A Tale of Adventure (1893)
- The Story of the Khartoum Relief Expedition (1894)
- The Story of the Uganda Mutiny (1895)
- The Romance of the Cape Frontier: A Story of Piracy and Adventure in Southern Africa (1897)
- The Land of Gold: A Tale of the Mining Days of California (1899)
- Pioneers and Patriots: A Page from the History of South Africa (1900)
- The Great North Land: A Story of Adventure in the Frozen North (1901)
- The Land of Riddles: A Tale of Adventure in Unknown Africa (1902)
- The New Land of the West: A Tale of Adventure in New Zealand (1903)
- The Red Book: A Story of Travel and Adventure in Russia (1904)
- The Golden Horde: A Tale of Adventure in Central Asia (1905)
- The Scarlet Runner: A Story of the Land of the Aztecs (1906)
- The Black Panther: A Tale of Adventure in the Brazilian Forests (1907)
- The Lost Continent: A Story of Adventure in Atlantis (1908)
- The Last of the Incas: A Tale of Adventure in Peru (1909)
- The Lone Rider: A Story of Adventure in the Wild West (1910)
- The Fighting Legion: A Tale of Adventure in Ancient Rome (1911)
- The Greenmantle: A Tale of Adventure in Central Asia (1912)
- The Yellow Fog: A Tale of Adventure in China (1913)
- The Lion's Share: A Story of Adventure in British East Africa (1914)
- The Trail of the Tiger: A Tale of Adventure in the Malay Archipelago (1915)
- The White Rajah: A Story of Adventure in Borneo (1916)
- The Sea Rovers: A Tale of Adventure in the Caribbean (1917)
- The Black Buccaneer: A Story of Adventure in the South Seas (1918)
- The Man from Madagascar: A Tale of Adventure in the Indian Ocean (1919)
- The Diamond Hunters: A Story of Adventure in South Africa (1920)
- The Elephant Hunters: A Tale of Adventure in Central Africa (1921)
- The Golden City: A Story of Adventure in South America (1922)
- The White Goddess: A Tale of Adventure in the Arctic (1923)
- The Black Magician: A Story of Adventure in India (1924)
- The Lost Colony: A Tale of Adventure in the New World (1925)
- The Red Emperor: A Story of Adventure in China (1926)
- The Blue Lotus: A Tale of Adventure in Tibet (1927)
- The Phantom City: A Story of Adventure in the Sahara (1928)
- The Crystal Mountain: A Tale of Adventure in the Andes (1929)
- The Sacred City: A Story of Adventure in the Himalayas (1930)
- The Hidden Valley: A Tale of Adventure in the South Seas (1931)